Radiation exposure system

Abstract

A system of radiography includes the provision of a cassette which is to be subjected to exposure from radiation beam. The cassette includes a screen layer and a filter layer having regions of different optical density and an imaging film. The filter acts to reduce the exposure of the film to the effect of radiation. The cassette is useful for dental images, particularly of the temporamandibular joint.

We claim: 
     
       1. A radiography apparatus having in overlapping relationship so as to define an area for exposure to a radiation beam, the apparatus comprising: a screen layer having areas of different reactance,   a radiation recording element for recording a radiation image caused by a beam directed to a subject, and   a filter layer, the filter layer having an area of first optical density and an area of second optical density, the filter layer being for regulating the effect of the exposure of the screen layer to a radiation beam over a selected area of the screen layer and the radiation recording element.   
     
     
       2. Apparatus as claimed in claim 1 including at least two screen layers, and wherein the filter layer is located between the screen layers. 
     
     
       3. Apparatus as claimed in claim 1 wherein the layer relationship in the direction from a source of the radiation beam includes the screen layer, the filter layer, and the radiation recording element. 
     
     
       4. Apparatus as claimed in claim 2 wherein the layer relationship in a direction from the radiation beam includes the screen layer, the filter layer, a radiation recording element and the second screen layer. 
     
     
       5. Apparatus as claimed in claim 1 wherein the screen layer includes areas of different reactant material, the areas of different reactant material selectively being graduated across the surface of the screen layer. 
     
     
       6. Apparatus as claimed in claim 2 wherein the screen layers include areas of different reactant materials, each screen layer being selectively graduated with varying reactant materials across the surface of the screen layer. 
     
     
       7. Apparatus as claimed in claim 2 wherein a first screen is of substantially consistent reactant material and a second screen is of a varying reactant material. 
     
     
       8. Apparatus as claimed in claim 1 wherein the filter layer includes an area of first optical density formed by a first material, and wherein the area of second optical density is an aperture in the material. 
     
     
       9. Apparatus as claimed in claim 2 wherein the filter layer includes an area of first optical density formed by a first material, and wherein the area of second optical density is an aperture in the material. 
     
     
       10. Apparatus as claimed in claim 1 wherein the area of second optical density is substantially a circular cutout in the filter layer, the circular cutout being substantially centrally located in the area of the filter layer. 
     
     
       11. Apparatus as claimed in claim 2 wherein the area of second optical density is substantially a circular cutout in the filter layer, the circular cutout being substantially centrally located in the area of the filter layer. 
     
     
       12. Apparatus as claimed in claim 8 wherein the screen layer is graduated in reactant material substantially regularly from a first end toward a second opposite end of the screen layer. 
     
     
       13. Apparatus as claimed in claim 10 wherein the screen layer is graduated in reactant material substantially regularly from a first end toward a second opposite end of the screen layer. 
     
     
       14. Apparatus as claimed in claim 1 wherein in a direction from the radiation beam the relationship of the layers is a radiation recording element, the filter layer and the screen layer. 
     
     
       15. Apparatus as claimed in claim 1 for use in dental radiography, and selectively for use in affecting radiation directed towards the temporamandibular joint, the radiation beam being an x-ray beam and the recording element being an x-ray film. 
     
     
       16. Apparatus as claimed in claim 2 for use in dental radiography, and selectively for use in effecting radiation directed towards of the temporamandibular joint, the radiation beam being an x-ray beam and the recording element being an x-ray film. 
     
     
       17. Apparatus as claimed in claim 1 for use in effecting radiation directed towards of a living subject, the radiation beam being an x-ray beam and the recording element being an x-ray film. 
     
     
       18. Apparatus as claimed in claim 2 for use in effecting radiation directed towards of a living subject, the radiation beam being an x-ray beam and the recording element being an x-ray film. 
     
     
       19. Apparatus as claimed in claim 1 wherein the filter layer is a material for minimizing passage of light in the wavelength spectrum range of at least one of blue or green, selectively to inhibit the passage of wavelengths in the range of about 440 nm to about 580 nm. 
     
     
       20. A radiography cassette comprising, in overlapping relationship so as to define an area for exposure to a radiation beam, a screen layer having areas of different reactance,   a film for recording an image caused by a radiation beam passing through a subject, and   a filter layer, the filter layer having an area of first optical density and an area of second optical density, the filter layer being for regulating the spectral response of the screen layer to radiation from a radiation beam over a selected area of the screen layer and the film.   
     
     
       21. A cassette as claimed in claim 20 including at least two screen layers, and wherein the filter layer is located between the screen layers. 
     
     
       22. A cassette as claimed in claim 21 wherein the screen layer includes areas of different amounts of reactant material that vary across the surface of the screen layer. 
     
     
       23. A cassette as claimed in claim 20 wherein the filter layer includes the area of first optical density having a first material, and wherein the area of second optical density is an aperture in the material. 
     
     
       24. A cassette as claimed in claim 20 wherein the area of second optical density is substantially a circular cutout in the filter layer, the circular cutout being substantially centrally located in the area of the filter layer. 
     
     
       25. A cassette as claimed in claim 23 wherein the screen layer is of reactant material that varies across the surface of the screen layer. 
     
     
       26. A cassette as claimed in claim 23 wherein the filter layer is a material for minimizing passage of lightwaves in the wavelength spectrum range that is substantially matched to the film. 
     
     
       27. A method of imaging a subject comprising the steps of locating a subject between a radiation beam and a cassette, the cassette including an overlaid relationship of at least one screen layer having areas of different reactance, at least one filter layer having at least an area of first optical density and an area of second optical density, and a radiation recording element for recording an image of the subject caused by the beam passing through the subject, the at least one filter layer being for regulating the effect of the exposure of the at least one screen layer to the radiation beam over a selected area of the radiation recording element, and wherein the sequence of the overlaid relationship of the at least one filter layer, the at least one screen layer and the at least one screen layer is effectively arranged in the cassette. 
     
     
       28. A method as claimed in claim 27 wherein the subject for imaging is selectively a human, and wherein an area for imaging is selectively the temporamandibular joint. 
     
     
       29. A method of recording images of a subject comprising of passing a radiation beam through a subject and recording the beam, the beam having passed through the subject, onto a film, the film being in layered relationship with a screen layer having areas of different reactance, and a filter layer, and the filter layer having different spectral responses over its area thereby, through the interaction of the screen layer, filter layer and radiation beam, acting to regulate the image recorded on the film. 
     
     
       30. A method as claimed in claim 29 wherein the different spectral responses are caused by different optical densities, the densities being related to the subject for radiation with the subject for imaging being relatively aligned with the film and the filter layer so that a predetermined image of the subject is obtained on the film, the image being coordinated with the different areas of the selected densities of the filter layer. 
     
     
       31. A radiography apparatus having in overlapping relationship so as to define an area for exposure to a radiation beam, the apparatus comprising: multiple screen layers, at least one screen layer having areas of different reactance,   a radiation recording element for recording a radiation image caused by a beam directed to a subject, and   multiple filter layers, at least one the filter layers having an area of first optical density and an area of second optical density, the filter layers being for regulating the effect of the exposure of the screen layers to a radiation beam over a selected area of the screen layers and the radiation recording element.   
     
     
       32. A radiography apparatus as claimed in claim 1 wherein the filter layer effects filtering through at least one of an electronic or chemical effect. 
     
     
       33. A radiography apparatus as claimed in claim 1 wherein the radiation recording element includes at least one of digital or chemical recording elements.